1. Field of Invention
The present invention relates to an apparatus for the filling of a medical filter and to a method therefor.
2. Description of the Prior Art
Such medical filters can be dialyzers, for example. Dialyzers can have a bundle of hollow fiber membranes which are enclosed in a housing and form a blood side and a dialysate side which are separated from one another by the plurality of hollow fiber membranes. Very generally, but in particular in dialysis, the problem must be faced before the putting into operation of a medical filter, in particular of a dialyzer, of completely deaerating or filling this filter. The filter is therefore prepurged with a liquid and thereby deaerated for the deaeration of the filter. With dialyzers, this is as a rule carried out during the setting up process of the dialysis machine using an isotonic saline solution (NaCl solution), with the NaCl solution being able to be admixed with an anticoagulant such as heparin.
In the preparation or filling of the filter and also of the extracorporeal blood circuit, the filter is often filled together with the hose system, for example in “continuous veno-venous hemodialysis (CVVHD)” or “continuous veno-venous hemodiafiltration (CVVHDF)”, such that the inflowing liquid initially runs in from below on the blood side with a dialyzer arranged perpendicular. The air is thus ideally upwardly displaced and e.g. conveyed into a waste bag via the upper venous connection of the dialyzer.
Since, in the counterflow process, the dialysate flows through the dialysate side with an opposite direction of flow in comparison with the blood side, the inflow and outflow at the dialysate side are arranged opposite to the inflow and outflow of the blood side of the dialyzer. On the filling of the filter, the problem thus arises that, with a filling of the dialysate side via the membrane from a blood side, in particular with a dialyzer arranged perpendicular, the outflow of the dialysate side is located at the lower end adjacent to the inflow of the dialyzer at the blood side so that on a filling via the membrane only a partial filling is adopted at the dialysate side. A complete deaerating is only ensured if the filter is rotated after the filling of the blood side and before the filling of the dialysate side.
This problem is solved in already known systems in that it is indicated to the operator to rotate the filter accordingly after the filling of the blood side. A further known solution approach consists of filling the blood circuit with a reverse connection by flow reversal on the blood side and hereby to make a rotation unnecessary. Such an approach is, however, complex and/or expensive since additional pumps and sensor devices are required.
It has furthermore been found that a filling of a filter with a rotary procedure enables a particularly reliable deaeration or filling of the filter. The procedure is established and recognized in clinics. It would therefore be desirable also to continue first to fill the blood side from the bottom to the top in order hereby reliably to displace the air from the blood side and then to rotate the dialyzer in order subsequently to deaerate and fill the dialysate side. This procedure of filling via the membrane from the blood side into the dialysate side furthermore has the advantage of also deaerating the pores of the membranes. In the normal case, the blood inlet in this process is at the upper end of the dialyzer during the later treatment. This arrangement is advantageous simply because the blood thereby does not have to be conveyed against gravity, which is accompanied by less stress for the blood. If, however, in this procedure, the rotation of the filter is forgotten after the prompt or if the dialyzer is already incorrectly connected from the start, the filling of the dialysate side can generally not take place completely and the effectiveness of the treatment drops due to reduction of the effective filter surface. Furthermore, in particular with systems which carry out a dialysate/filtrate balance by means of scales, alarm messages/triggering of alarms can occur due to residual air entry into the balancing containers. Further disadvantages consist of the fact that coagulation can be stimulated by remaining residual air in the filter in the later treatment which could result in partial clogging of the membranes.